Basement plumbing design

[eodschulte]

My house was built three years ago (in South Dakota) and, unfortunately, we weren't around when it was built. We are looking at finishing the basement, but I'm a little confused on what they've left me. In the picture you can see two stub ups as well as the main drain that is coming from the other two 1/2 baths and the laundry room (all upstairs). The tub is also roughed in. I dug down in the box and found a 2" line running horizontally. The smaller of the two pipes is also 2" and the other is 3". In the other picture, you can see the line coming down from the kitchen sink (going into the slab) as well as a 2" capped line (along the joists--you can see it start but the end is blocked by the wall.)

Here's what I know (or at least I think I know):
the capped line running horizontally is for future venting..
The 3" is for the toilet
The box is for the tub. The way I have it drawn out, it should be a right drain set-up.
The other 2" line is for the vanity.

I'm a bit confused on how to properly vent everything. Any suggestions would be greatly appreciated. I also included a copy of the floorplan that we got from the builders.

Thanks in advance for the help.

-Nick-

[hj]

The 3" is for the toilet, the 2" is the vent for the toilet and the lavatory drain. The tub needs a "P" trap on the end of the horizontal line, BUT, there does not appear to be a vent for the tub and in most areas the trap would be too far from the sink/toilet to install without a vent. IF it were changed to a left hand tub, depending on how the horizontal pipe is run, it might be close enough, (but on the other hand if it goes directly to the "P" trap it would not make any difference in the length). Vecause of the main house drain, your layout will probably have to be, toilet on the left, vanity in the center and the tub on the right.

[eodschulte]

Thanks for the response. The tub vent was the one I was worried about. I wasn't sure if it would count as a vent if the tub was connected (underground) to the 2" vanity/vent (I've seen some people say there is a max distance.) I'm not sure how to vent off the drain/p-trap in the boxed area that they left open for me otherwise.

Additionally, the way they have it laid out in the floorplan, it appears that the vanity would go on the left and will have to have a line running from the sink trap over to the drain/vent. There won't be enough room to try and squeeze a vanity in between the toilet and the tub.

[cacher_chick]

This kind of a situation never surprises me, as what the original plumber might have had in mind is never what the person later living there envisions for a basement bathroom. More often that not the solution is to break some concrete and plumb the bath for the layout the you want. It's not that big of a deal to do, and will make for much greater satisfaction in the end.

[hj]

To my mind, it will be even harder to squeeze a lavatory between the toilet and the upstairs drain line because there will have to be at least 15" from the center of the toilet to the sink cabinet, and there does not appear to be anywhere NEAR the minimum 39" it would require for even a 24" sink cabinet.

[eodschulte]

The upstairs drain line wont even be in the bathroom. It will be in a bedroom closet (with access to the cleanout.) The wall that has the 4" will actually be off the cement wall by a good bit. The cleanout of the 4" pipe will essentially be where the face of the bathroom wall is. I assume that is the plan sice there is a little over 12" to centerline of the 3" pipe. If you look at the second picture, you can actually see another partial wall. That is the leading edge of the bathroom (where the door will be located.) I added a different sketch.